Conventionally, a method of obtaining a molded product by curing a resin which is produced by metathesis polymerization of a cycloolefin and the like has been known. For example, a method of preparing a thermoplastic resin such as a thermoplastic norbornene resin by solution polymerization and crosslinking the thermoplastic resin using a crosslinking agent such as an organic peroxide to obtain a crosslinked molded product, a method of reacting cycloolefins which can be polymerized by metathesis polymerization in the presence of a carbene complex such as ruthenium without using a solvent to obtain a half-cured molded product and laminating a copper foil on the resulting half-cured molded product by press-heating to obtain a copper-clad laminate, and other methods have been proposed.
As the former method of obtaining a crosslinked molded product, Japanese Patent Application Laid-open No. 6-248164 describes a method comprising preparing a homogeneously dispersed norbornene resin composition by adding 0.001-30 parts by weight of an organic peroxide to 100 parts by weight of a thermoplastic hydrogenated ring-opening norbornene resin and adding 0.1-10 parts by weight of a crosslinking agent to one part by weight of the organic peroxide, forming the composition into a film or prepreg, laminating the film or prepreg on another material (substrate), and crosslinking by fusing the resulting laminate by heat-press to obtain a crosslinked molded product. The patent specification describes that the crosslinked molded product exhibits excellent heat resistance, solvent resistance, chemical resistance, moisture resistance, water resistance, and electrical properties and is useful as an interlayer dielectric, a film for forming a moisture-proof layer, and the like.
However, the proposed method requires process steps of applying a thermoplastic resin composition solution to a substrate, removing the solvent to obtain a sheet, peeling the sheet from the substrate, and layering the sheet on a copper foil or the like, followed by a heat press operation. The method is complicated due to the many process steps and is not necessarily advantageous for manufacturing on an industrial scale. Moreover, the copper foil may be peeled off due to a residual solvent or may blister due to a gas generated from the solvent.
As the latter method of manufacturing a copper-clad laminate by metathesis polymerization of cycloolefins, Japanese Patent Application Laid-open No. 2001-71416 describes a method of preparing a semi-cured curable molded material by reacting metathesis-polymerizable cycloolefins in the presence of a carbene complex of ruthenium or osmium, placing a copper foil on at least one side of the molded material, and applying heat-press. This method has made it possible to efficiently manufacture a copper-clad laminate using a press-forming machine by dividing the process into a first step of obtaining a curable molding material in a half-cure state in which the polymerization (metathesis) reaction of raw material cycloolefins is not completed and a second step of completely curing the resulting molding material with heating.
However, this method has a drawback of unduly worsening the working environment due to an unacceptable odor of unreacted monomers when preparing the half-cured molding material. In addition, the hardness of the molding material may change due to a continued polymerization reaction while the material is stored in the half-cured state, making it difficult to obtain a copper-clad laminate with a desired form.
Japanese Patent Application Laid-open No. 11-507962 discloses a method which comprises polymerizing cycloolefins in the presence of a ruthenium-carbene complex and a crosslinking agent by metathesis polymerization to produce a polycycloolefin and post-curing (post-crosslinking) the polymer.
However, when the method taught by the patent specification is followed by heat-pressing the norbornene resin-copper foil laminate obtained by this method, only a cross-linking reaction proceeds without the resin before the post-cure being melted or fluidized. For this reason, it is difficult to produce a copper-clad laminate with excellent interlayer adhesion.
In view of this situation, an object of the present invention is to provide a post-crosslinkable thermoplastic resin and a method for manufacturing the same, the thermoplastic resin being obtainable by bulk polymerization of cycloolefins in the presence of a metathesis polymerization catalyst, and being free from a problem of an odor due to residual monomers, excelling in fluidity during melting with heating, and storage stability. Another object of the present invention is to provide a crosslinked resin and a method for manufacturing the same, the resin being obtained by crosslinking the above thermoplastic resin and excelling in electric insulation properties, mechanical strength, heat resistance, dielectric property, and the like. Still another object of the present invention is to provide a method for manufacturing a crosslinked resin composite material, and the composite material being obtained by laminating the thermoplastic resin of the present invention on a substrate and crosslinking the thermoplastic resin, excelling in adhesion between the crosslinked resin and substrate, and useful as an electrical material and the like.